The present invention relates to a seat belt retractor to be mounted in a vehicle.
In the related art, a seat belt device that has various structures is known for restraining a vehicle occupant by means of a seat belt in a vehicle, such as an automobile.
Japanese Unexamined Utility Mode Registration Application Publication No. 6-71333 (hereinafter known as the '333 reference) discloses a structure of a seat belt device, which retracts and withdraws the seat belt by driving a motor. The technology in the '333 reference employs a structure that retracts and withdraws the seat belt through the use of a spool driven by a motor. The tension of the seat belt is intermittently varied by driving the motor, and thus the restraining force can be varied. Accordingly, it is possible to warn a driver with respect to a vehicle collision.
However, when the warning is conducted by the seat belt device disclosed in the '333 reference with respect to a vehicle collision, the seat belt has an initial slack, and thus a part of the rotation of the motor is used to remove the slack at the time of an initial operation. Accordingly, it is impossible to obtain the desired belt tension that is useful to warn the vehicle occupant.
The present seat belt retractor has been made to solve the above-mentioned problem. It is an object of the present disclosure to provide an effective technology that is useful to reliably warn a vehicle occupant by using the seat belt of a seat belt retractor to retract/withdraw the seat belt depending on the driving of the electric motor.
The invention is provided to address the above-mentioned problem. Although the invention can be typically applied to a seat belt retractor mounted in a vehicle such as an automobile, the invention can be applied to a structure of a seat belt retractor that is mounted in a vehicle other than the automobile, for example, an airplane, a ship, an electric train, a bus, and so on.